Radio receiving and transmitting system



March 19, 1946.

RADIO RECEIVING AND TRANSMITTING SYSTEM [Mamma/gall #afin/Wer Filed Aug. 22, 1941 2 Sheets-Sheet 1 Marl/ary Y ,a

luz/Yigg Piece/ler March 19, 1946.

INSON RADIO RECEIVING AND TRANSMITTING SYSTEM Filed Aug.

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ar slang/a Aww fallan/Wer?" 2 Sheets-Sheet 2 Wwe/)fer ar sy//d/r raf/1 traf/sniffer www @044, mwmw bte/ww 2W MAM* Patented Mar. 19, 1946 RADIO RECEIVING AND TRANSMITTING vSYSTEM James Robinson, London, England Application August 22, 1

In Great Brlitai 6 Claims.

This invention relates to radio receiving and transmitting systems.

According to the present invention there is provided a radio system comprising means for receiving signals from a separate or distant transmitter, and an auxiliary transmitter or radiating means for like signals of the same frequency and energised by or under the control of the received signals, wherein the total or resultan-t retroaction between the radiating and receiving means is of negative sign. The negative retroaction may be obtained by a physical connection or coupling between the radiating means and the receiving means or by a wireless link operating at a frequency different from that of the received and re-radiated signals aforesaid. Preferably, the retroaction is wholly or mainly btained by reception at the receiving means of the signals transmitted by the radiating meansthrough space. When the aerials of the receiving and radiating means are close together due regard must be paid to the induction eld at the receiving means in addition to the radiation eld of the radiating means in determining retroaction in the negative sense.

One application of the invention is toa system in which the eld strength of a radio transmission is intensied or boosted at a point spaced from the transmitter and in one manner of carrying out the invention the receiving means and the radiating means constitute a boosting or relay station for intensifying locally the eld strength of the separate transmitter, either to assist reception in the locality or to provide an additional transmission combining with the other or that of another such boosting station to produce a beam cr other directional `transmission for reception at a distant place. By providing negative retroaction between the radiating means and the receiving means in which the phase difference between the primary and retroactive signals is between 90 and 270", an improvement in stability of the boosting or relay station is obtained. The system may include additional transmitters and/or radiating means spaced from the others; for providing a local intensication of eld strength the phase relationship may be indiscriminate but for a beam or other directional transmission appropriate phase relationship of the transmissions is required.

The signals from the separate transmitter `ind from the auxiliary transmitter means produce an interference pattern and the use of negative retroaction between the radiating means and the receiving means operating `or radiating 941, serial No. 407,977 n May 2, 1940 ference from .these transmissions.

lor more positions may with a phase difference ,of substantially determines the existence of a trough inthis interference pattern passing through the position of the receiving means, and consequently determines the positions yof the troughs and crests throughout the interference pattern. In this way, one readily be pre-selected at which the eld strength of the separate transmitter is reduced to a minimum. Thus, for a given `position of the separate transmitter and transmission frequency the positions of the troughs and crests of the interference pattern are determined by the position of the receiving means.

In my copending application for United States Letters Patent Serial No. 407,976, led concurrently herewith, there is described a radio receiving system in which an auxiliary transmitter or radiator operating at the same frequency as a separate transmitter is employed to produce an interference pattern and in which a receiver for other signals at the same or adjacent frequency is so located, having regard to the form of Acollector used, with respect to the interference pattern as to be free or substantially free of intera further feature of the present invention this auxiliary transmitteror radiator is constituted by the receiving .and radiating means of the present invention, and a receiver for another wanted transmission is so located, having regard to the form .of aerial used, in the interference pattern predetermined by the receiving and radiating means with negative retroaction, that interference from the separate transmitter is considerablyreduced. The receiving and radiating means of the present invention may thus be employed as the auxiliarytransmitter or radiator in any of its applicationsdescribed in my copending application hereinbefore mentioned.

VWith the use of negative retroaction as aforesaid and .the location of the receiver for the wanted transmission in the neighbourhood of the receiving means, a trough in the interference pattern is obtained for this neighbourhood as a result of unwanted transmissions from separate or distant .transmitters arriving from various directions. A further feature of the invention consists vin providing .the Areceiving means with a directional aerial zso that the field of unwanted transmissions is. reduced A,only for transmissions arriving from a given Vdirection or directions.

In ,a .further manner of carrying out the invention the receiving and radiating lmeans are arranged in line with a separate or distant trans- According toV rate or distant transmitter. In one use of thisl arrangement in which the power of the radiating means may be considerably less than that of the transmitter a zero resultant field will be obtained at a place spaced from the radiatingL means in this direction and the receiver for other wanted transmissions is located at this place. In another use of this arrangement fory boosting purposes in a power comparable with that of the transmitter, the two transmissions which augment one another in the opposite direction together provide a directional or beam transmission in that direction. 1

According to another manner of carrying out the invention for boosting the transmission from the separate or distant transmitter, there are employed in addition to a boosting transmitter and a receiver for energising or controlling the boosting transmitter, receiving and radiating means with negative `retroac'tion as aforesaid for providing in conjunction with the boosting transmission an interference pattern enabling the receiver of the boosting station to be positioned so as to operate with minimum interference from theA boosting transmission,

VIt can be shown that in an arrangement for negative retroaction as aforesaid if, due to some cause either owing to the initial adjustment or to variation of the adjustmenhthe retroactive .signals are not directly opposed in phase to the incoming signals applied to the receiving means from the separate transmitter, then there will be ashift of phase of the radiated signals towards the condition in which there is true phase opposition. "lhus,since the primary input signals at the receiving means depend upon the separate transmitter, it will be seen that any givenrphase relationship between the signals from the separate transmitterand the signals provided by the radiating means will be substantially maintained. This automatic control of phase relationship will thus operate for any changes which may take place either at the separate transmitter or at the radiating means, and ywill largely ensure the troughs and crests of the interference pattern being maintained at given places. Thus, by means of the phase control provided by this invention the interference pattern is maintained stationary or substantially stationary in space so as to maintain the interference-free conditions for the operation of the receiver for other signals at various points in the held.

Specific embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figures 1, 2, 7 and 8 are diagrams representing systems for receiving transmissions in the strong field of another transmission on the same or adjacent frequency, and

Figures 3 to 6 are diagrams showing boosting systems embodying the invention.

Referring to Figure 1 of the drawings there is indicated a transmitter A providing a strong field for an area in which it is desired to receiveother transmissions, particularly on the same or adjacentfrequencies. To provide facility for receivwhich the radiating means lmay have ing other transmissions there is set up an auX- iliary transmitter or radiator B for delivering the same frequency of transmission as given by the transmitter A, as described in my copending application hereinbefore mentioned. The two transmissions which are thus of identical frequency produce an interference pattern so that a combined or resultant eld in two transmissions varies from place to place yto form troughs at places of minimum or zero value indicated at X in the drawings and crests at other places. The positions of these troughs and crests depends on the separation of the transmitters and the phase l relationship of the transmissions.

With the apparatus of the present invention the auxiliary transmitter or radiator B is controlled by a receiver R for the signals transmitted from the transmitter A. Thus as shown in Figure 1 the received signals may be simply amplified by the receiver R which energises the transmitter B or the received signals at R may be employed to control a self-contained transmitter B.

In both Figures 1 and 2 the signals at the receiver R are fed to control or energise the transmitter B by means of a link indicated at a which may be constituted by a conducting line or `by a wireless link, or in the case where the receiver R and the auxiliary transmitter B are close together, by an electric connection or coupling between the associated receiver and transmitter apparatus. In addition, a retroactive coupling is provided between the auxiliary transmitter B and the receiver R operating in the sense to provide negative retroaction. This retroactive connection or coupling is indicated by the dotted line at B and is provided by the pick-up at the receiver for the signals radiated from the transmitter B. Alternatively, it may be constituted by a conducting line as shown in Figure 3 or by a wireless link operating at different frequency. With the use of negative retroaction the disposition of thefinterference pattern is predetermined for a given condition of operation by the position of the receiver R, and furthermore this disposition of the interference pattern is substantially maintained in spite of the variations of phase which may Voccur in operation. While the spacing between the receiving and radiating means may be the chief factor in determining the phase of retroaction it will be understood that the forms ofV aerial and couplings used must also be taken into consideration. By varying the retroaction phase a control is obtained for the positions of theN troughs and crests of the interference pattern.

'I he two transmitters A and B radiate waves of identical frequency and thus an interference pattern is produced with crests and troughs at c-ertainpositions. The position of these crests and troughs depends on the relative phase of the two transmitters, and by changing the phase of one of the transmitters the positions of the crests andtrcughs are changed. Troughs are obtained where the phases from the two transmitters are at 180, whereas crests occur where identical phase relationship exists. As the transmitter B is energised by waves which the receiver R obtains'from. the other transmitter A some control of the position of troughs is obtained by chang-v ing the positions of R and/or of B. In order to avoid interference, it is necessary to choose conditions such that the receiver R is at a trough of the interference pattern and thus this condi-V tion is vobtained if the waves received originally .at R are constrained to feed the transmitter B which returns-"them 'to *the fkrcaliity'-'cifil'ue'receiver -waves from Aand lB Vare -inpppos'i-te 1.phase Aat the receiver R. One Avsuch condition'-is*theslec- Ation of a suitable distancelbe'tween RandfBwhich would be a quarter of l'a Wavelengthfifno y'other phase changes lwere introduced. Another --m'eans for changing lthisphase is vrto alterthe tuning of 'one or more of the rcircuits inRand/or'B. Also, by 'changing the length of vl). Thefcondi'tionto 'be satisfied is Ato lhave the -receiver *R Lat a 1trough and in the present instance, there lis still nanother condition'which gives some control and r'this is thepretroaction which 'can Voccur"between"Rand B, vfor the receiving aerial at"R can receive -`waves from both transmitters. Thus, 'averypower'fu'l control of the phase can "be `obtained by 'controlling thisretroaction. 'One method ofrloritrolling the `Vamount of retroaction is 'togive the 'receiving aerial at R directional properties'asv shown in vFigure liso that itcanrreceive predeterminedratios of 'the 4waves from A'and B. For example, .the

receivercan be arranged tolo'b'tain much'less from yBthan 'from A or vice' versa.

The phase maybe adiusted'toibe exactly 180 by `altering the distance between 'Rand B, or by adjusting the lengths ofthe cables which "feeds B or by altering thetuning of one ofthe circuits. The idealis to make ,this'phase asnearly180 as'possible in order to ensurethat theLreceiver is in a trough of the interference ,pattern, 'but in `practice there may be deviations df some :degrees from 'this ideal conditiomwhen the feedback 'will beat a phase 'which is `not exactly negative. `"It can be shown mathematically that retroaction under these conditions has -the property that it directional vaerial providing 'a minimum vin 'fthe direction of the :transmitter A to stil'l 'further reduce .interference Afrom ,the transrriitter A fin cases Where the wanted .transmission orrtransniissions arrive .from other directions.

In Ythe arrangement shown @inl-Figure, the radiator B for signals received "by V.the rreceiver Ris arrangedin line with and betweenithe transmitter A .and the receiver R. En 7this-case lthe .receiverR is spacedlfromthe radiator 1B byfone-Y quarter of a wavelength.. or-by.an\oddmultiplenof Vone-quarter of a wavelengthfso thatithe signals radiated from the radiator `B lwillfbe opposed fin phase with the signals from the-.transmitterA assuming no other phase change is introduced as for-example by vthe .characteristicsrof .the apparatus. For the vpurpose of reducing .interferencethe power of the radiator Bfmaybe lowcom- Apared Awith that of the ,transmitter.Asoethatnt some positions spaced frorn B in ,the direction .of the arrow the total signal` trength willlbe `zero.

'The receiver` ris therefore,p ositionedat'this p oint so .as to be V'free of interference` from ythe .transmitter A and the .radiator`B logether.

In van application Yof `the invention to`,.boostin g w or relay station such a station may be constiu 111g VJtuted by a .receiver 1R and a .radiator vB v'as :described 4with 'reference to Figure 1 or 2. ABypromviding :negative 'retroaction between the radiator `B andthe receiver R complete Astability of the Vvsystem maybe obtained.

The A`preserit'inventi'on may furthermore be applied to -alboosting or `relay system as described in "my rcopending application hereinbefore menlti'oned,and in'Figure 3 there is 4showna primary ltransmitterT and lat a position remote therefrom a boosting transmitter A operating at the same frequency. This boosting transmitter A is `ener- -gised `by `means of a receiver R receiving the transmission'from the primary transmitter T and lcontrolling or energizing the boosting transmitter A. In lorder that the receiver R shall ynot be `affected to an appreciable extent by the transmission radiated from the boosting transmitter A 1vthere'is provided an auxiliary transmitter B providing 'in combination with the transmitter A an interference pattern as Vabove described and "the receiver R is'so positioned having regard to theform of collector used that the resultant of the signals obtained from the transmitters A and `B is aminimum.

The vreceiver R is connected with the auxiliary ltransmitter B through two channels a. and b, the "'former'for loperating the transmitter B and the latter `for providing negative retroaction between the transmitter B and the receiver R, as herein- 'before described; The receiver R is also suitably `coupled as indicated atc with the boosting transmitter A. Thus,'by the addition of the means :for negative` retroaction instability resulting. from the possible 4positive retroaction between the transmitter and receiver is further reduced and, moreover, there is obtained an automatic con- Atrol of the interference pattern to prevent shifting of the troughs or crests of this pattern which might otherwise upset the Voperation of the boost- 'ing station comprising the transmitters A andB and the receiver R.

Yet afurther application of the invention to a 'boosting or relay system is shown in Figure 4. In this case the .boosting transmitter A is energised or controlled by the receiver R which receives signals fromthe primary transmitter T, the coupling being indicated at c. In addition, there is, provided an .auxiliary transmitter B energised or controlled by anauxiliaryreceiver R' through a channel-indicatedfby a, and negative retroaction .as indicated by b isprovided between the auxiliary transmitterjB and the receiver R'. AR ,picks uprsignalsfrom both the transmitter T and the boosting transmitter Aand delivers these signals to the auxiliary transmitter B', thenegaltive retroaction .providing for the stable operationgof the treceiver R and the auxiliary trans- `mitter .B. 'The transmission from the auxiliary transmitter B' combining with that from the Vboosting transmitter A produces `an interference pattern and the receiver R feeding the boosting transmitterA asindicated at vc is solocated with respect tothisinterference pattern as to be substantially free from interference from the transmission fromA and B', although capable of receiv- 'ing thetransmission from the transmitter T.

4It twill be seen rin Ythe arrangement shown in Figure 4 that .with .negative retroaction between the auxiliary ,transmitterB' `and the receiver R' the transmissionslfrom A and-B mustbenopposition so that by making the auxiliary transmitter .B `of adequate l power ,a directional form `of translmission,isrobtained .Oneor more additional booststations in any of the forms` above described The receiver may be provided so as to form together a highly directional or beam transmission system.

In some cases, where there is obtained an interference pattern for the purpose of enabling a reduction of interference to be obtained, it may be desirable to provide an even further reduction of such interference. This may be achieved as shown in Figure 5 by providing another receivingmeans R' having an aerial I6 so selected according to the place Ain the interference pattern produced by A+T,'that is to say, either a crest or trough in which it is situated, providing a minimum respouse for the resultant transmission, and two auxiliary transmitters A', B controlled or energised by the output of this receiver and spaced apart at opposite sides of the receiver. Negative retroaction b is provided between these auxiliary transmitters and the receiver so that the phase of the signals delivered by these auxiliary transmitters is in opposition to the transmissions producing the aforesaid interference pattern. There isY thus obtained a further interference eiect which serves to further reduce the total effective signal strength at the position of the receiver.

The retroactively coupled receiving and radiating means may comprise a unitary apparatus as shown by the dotted lines in Figure 1 having both a collector for incoming signals and a radiator for outgoing signals delivered under the control of the received signals.

In some circumstances either in boosting or receiving it is preferable to provide appreciable spacing between the receiving means and the radiating means and such spacing may be used to produce the required phase relationship between the signals applied to the receiving means from the auxiliary transmitter B and the fed-back signals from the radiating means, either alone or in conjunction with phase controlling means I ll as in Figure 2 in connections between the receiving means and the radiating means. Thus, in order to obtain the required negative retroaction it is Y convenient to place the receiving means at a position approximately one-quarter or an odd multiple of one-quarter of the wavelength from the radiating means; the longer spacing may be preferable to avoid any difliculties arising from the induction field of the radiating means. In order to provide for control of the phase of retroaction means such as a loop aerial Il as shown in Figure 3 or search coil may be employed at the receiver in which the negative retroaction is to be eiected. Thus, by slight rotation of the loop or search coil the appropriate phase of retroaction may be Ysimply achieved and also control of the amount of retroaction may be obtained.

The combined signal strength at a trough of the interference pattern depends not only on the relative phase of the signals but also on their relative amplitudes. Thus, it may be required in some circumstances to employ only a small negative retroactive eiect and in order to obtain this result the collector of the receiving means, which also receives feed-back signals from the radiating means, may be of a directional character arranged for a minimum response in the direction of the radiating means. Thus, in the case where the receiving means is not in line with the separate transmitter B and radiating means, this collector may consist of a loop II arranged approximately at right-angles to a line joining the collector with the antenna for the auxiliary transmitter, as shown in Fig. 3.

A unidirectional collector (as distinct from a loop which receives equally in opposite directions) lmay alternatively be employed to provide a similar ceiving the retroaction signals from the radiating means A respectively. One or both of such antennae will be of a directional character so that it is effective only for the transmission to which it is allocated.

Also, for the purpose of providing the required relationship between the amplitudes of the signals at a given point positiveretroaction may be employed in addition to the negative retroaction. Thus, for example, the receiving means mai7 in itself have positive retroaction provided by the line i5 in addition to the negative retroaction b between the radiating means see Figure 7 and the receiving means.

In the case of a receiver to be placed on a trough in the interference pattern aforesaid so as to be free of interference from the transmissions produced by the separate transmitter T and the radiating means, the resultant field strength produced by these transmissions at the trough may be further reduced by employing a directional aerial for this receiver. Thus, the aerial is such that it receives more efficiently from the stronger transmission than from the weaker one, having regard to their field strengths at the receiver. Instead of signals originating from a single separate transmitter they may be derived from two or more transmitters T1 and T2 as shown in Figure 8 which may be' arranged especially to give a di rectional distribution. These transmitters in themselves produce an interference pattern which enables a receiver to be placed in a position of minimum response and the radiating means and receiving means aforesaid may be employed still further to reduce the resultant signal amplitude at a trough in this interference pattern. Furthermore, more than one radiating means may be employed for reducing the resultant field strength at a trough in the interference pattern.

Such radiating means which are spaced apart may be operated by the same or independent receiving means. Thus, for example as shown in Figure 5, there may be two or more boosting transmitters A A energised from independent receiving means R R and arranged in line with auxiliary transmitters B B to produce a directional transmission. The separation between each auxiliary transmitter and boosting transmitter may thus be a half-wave length. The boosting or relay station may be provided to give local reception or a plurality'of such boosting stations may be employed in suitable spaced relationship to provide a beam or other directional transmission for positive reception. f

I claim:

1. A radio system comprising at a receiving station a receiver for wanted signals, a receiver for unwanted signals which are required to be suppressed, a transmitter energized by said latter receiver so as to radiate signals of like frequency to the unwanted signals, and so as to produce a eld pattern having zones of minimum intensity, which receiver for wanted signals is located. in one such zone and means acting between the re- .76 ceiver of unwanted signals and the transmitter it energises to produce negative retroaction stabilising the said eld pattern.

2. A radio system comprising at a receiving station a receiver for wanted Signals, a receiver for unwanted signals which are required to be suppressed, a transmitter energised by said latter receiver, so as to radiate signals of like frequency to unwanted signals, and so as to produce a field pattern having Zones of minimum intensity, which receiver for wanted signals is located in one such zone and means acting between the receiver of unwanted signals and the transmitter it energises to produce negative retroaction stabilising the said eld pattern, which meanslare constituted mainly by the signals transmitted through space.

3. A radio system comprising at a receiving station a receiver for wanted signals, a receiver for unwanted signals which are required to be suppressed, a transmitter energised by said latter receiver, 'so as to radiate signals of like frequency to the unwanted signals, and so as to produce a field pattern having zones of minimum intensity, which receiver for wanted signals is located in one such Zone, an antenna for said receiver, which antenna is so positioned in the interference pattern in accordance with its phase that it is in a neutral zone, and means acting between the receiver of unwanted signals and the transmitter it energises to produce negative retroaction stabilising the said field pattern.

4. A radio system comprising at a receiving station a receiver for wanted signals, a receiver for unwanted signals which are required to be suppressed, an auxiliary transmitter energised by said latter receiver, so as to radiate signals of like frequency to the unwanted signal, which auxiliary transmitter and latter receiver are arranged in line with the transmitter of unwanted signals with the auxiliary transmitter between said latter receiver and the transmitter of unwanted signals, so as to produce a field pattern having zones of minimum intensity, which receiver for wanted signals is located in one such zone and means acting between the receiver of unwanted signals and the transmitter it energises to produce negative retroaction stabilising the said field pattern.

5. A radio boosting system comprising means for receiving signals from a transmitter of signals to be boosted, a boosting transmitter, means for energising said boosting transmitter from said receiver, an auxiliary transmitter operating on the same frequency as the boosting transmitter, means for energising the auxiliary transmitter from said receiver, so as to produce a eld pattern having a zone of minimum intensity in which said receiver is located, and means acting between the receiver of unwanted signals and the transmitter it energises to produce negative retroaction stabilising the said field pattern.

6. A radio boosting system comprising means for receiving signals from an external transmitter of signals to be boosted, a boosting transmitter, means for energising said boosting transmitter from said receiver, an auxiliary transmitter operating upon the same frequency as the boosting frequency, an auxiliary receiver responsive to the signals of the external transmitter and boosting transmitter, and controlling the auxiliary transmitter, so as to set up a field pattern between it and the boosting transmitter, having Zones of minimum intensity, which rst said receiver is located in one such zone, and means acting between said auxiliary receiver and said auxiliary transmitter to produce negative retroaction stabilising said field pattern,

` JAMES ROBINSON. 

